Because intelligence is an individual trait that is totally not under control of a person. It will not work this way for a long even if person is smart. Especia

Because intelligence is an individual trait that is totally not under control of a person. It will not work this way for a long even if person is smart. Especially if she is smart: she will see that to believe that "smart means good" is stupid (what means to be smart? to have good grades? to create a successful startup? to speak smart things? to hear others praise your smartness). So person will risk to start obsessing about smart behaviour, overcontrolling impulses, think twice before opening your mouth, a mistake is a fail that damages self-esteem, and so on... It can be good when you manage to find some unexpected creative and smart idea, but it is fun even without self-esteem: insight in any case is rewarded by brains. But creativity is an ability to generate a whole lot of ideas, stupid and smart, what would you do if your brain stopped to generate any idea in a fear to generate a stupid one? To be smart is to find non obvious idea, but to find a good idea you need to think a lot, and no rewards while you are thinking. Frustration is the common state of good thinker, and frustration itself seems from inside as inability to solve problem, as a lack of intelligence. You are working hard, but the only visible result is inability of your intelligence to solve the problem. You can fight with fatigue for some time, but if a hard work is not rewarded by you brains as a prove that you are a good boy, then this time can be too short to actually solve the problem. You should belive that you are smart unconditionally. And if sometimes you are start to doubt it, it should not be a big deal for you. Our society force people to believe that smart is good and stupid is bad, so we are subjects of a narrative that "if you are stupid, then you are bad boy. Go to your room!". There is no need for parents to make special efforts to make this narrative more powerful in your head.